Thin-film silicon devices include thin-film silicon solar cells. In the related art, the use of crystalline silicon films is known in the field of thin-film silicon solar cells. For instance, considering a tandem solar cell as an example, which is one class of multi-junction solar cell in thin-film silicon solar cells, in this tandem solar cell, a layer called a bottom cell is formed between a top cell and a rear surface electrode. The bottom cell has a photoelectric conversion layer with a pin structure, and crystalline silicon is used for the i layer. The crystalline silicon is a thin film in which minute crystals and amorphous regions are present in a mixed state.
Heretofore, one example of a known film quality evaluation method for crystalline silicon is an evaluation method using a Raman peak intensity ratio in a Raman spectroscopic method (for example, see Patent Document 1).
In particular, Raman spectroscopic measurement is performed for crystalline silicon using a Raman spectroscopic analyzer to obtain a ratio (I520/I480) of intensity I520 of a Raman peak indicating a crystalline state (in the vicinity of a wavelength of 520 cm−1) to intensity I480 of a Raman peak indicating an amorphous state (in the vicinity of a wavelength of 480 cm−1), and the film quality of crystalline silicon is evaluated using this Raman peak intensity ratio (I520/I480). The Raman peak intensity ratio can range from 0 to infinity by definition. When the Raman peak intensity ratio is 0, the silicon is considered to be amorphous, and as the Raman peak intensity ratio increases, the degree of crystallinity of a crystalline silicon film is considered to increase.
In the case of crystalline silicon used for a solar cell, a proper range of the Raman peak intensity ratio is determined in accordance with the required quality, and for example, the film quality is evaluated based on whether a measurement value of the Raman peak intensity ratio is within this proper range or not.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-26348